Proximity sensor arrangement in a mobile device

ABSTRACT

A radiation passing layer has a top surface and a bottom surface below which a proximity sensor is positioned. A radiation shield is between the emitter and the detector, and extends to the bottom of the radiation passing layer. A radiation absorber being a separate piece and of a different material than the shield is positioned to provide a radiation seal between the top surface of the shield and the bottom surface of the radiation passing layer. Other embodiments are also described and claimed.

FIELD

An embodiment of the invention is directed to a proximity sensorarrangement used in a handheld mobile communications device. Otherembodiments are also described.

BACKGROUND

In the field of personal mobile devices such as laptop computers, tabletcomputers, and smart phones, proximity sensors are used to sense hoverevents. These are no touch, close proximity positioning of parts of theuser's body or other objects (e.g., a stylus held by the user), near anexternal surface of the device. Typically, such proximity sensors aredesigned to detect an external object that is located outside the nearfield detection capability of a touch sensor (e.g., those used in atypical touch screen display such as found in an iPhone™ device by AppleInc.). In one instance, the proximity sensor includes an infraredemitter and a counterpart infrared detector that are controlled andsampled by proximity sensor circuitry integrated in the housing of themobile device. Emitted infrared radiation is scattered by the externalobject, and then detected and analyzed to infer that an external objectis (or is not) close to the exterior surface. In the case of handheldmobile communications devices, the sensor may be located near anacoustic aperture for an earpiece speaker (receiver) of a mobilecommunications handset, and is used to determine when the handset isbeing held close to the user's ear, as opposed to away from the ear.When the proximity sensor indicates that the external object, in thiscase, the user's ear or head, is sufficiently close, then apredetermined action is taken, including, for example, turning off ordisabling a touch screen display that is on the same external face ofthe housing as the acoustic aperture. This, of course, is designed toavoid unintended touch events caused by the user's cheek, while thehandset is held close to the user's ear during a call.

SUMMARY

An electronic device having a proximity sensor assembly includes aradiation passing layer having a top surface and a bottom surface. Aproximity sensor having an emitter and a detector is positioned belowthe radiation passing layer. A radiation shield positioned between theemitter and the detector extends to the bottom surface of the radiationpassing layer. A radiation absorber, which is a separate piece and of aseparate material than the shield, is positioned to provide a radiationseal between a top surface of the shield and the bottom surface of theradiation passing layer. By virtue of its radiation absorptioncharacteristics, together with its positioning and contact with thebottom of the radiation passing layer, the absorber may help preventstray radiation from the emitter that may have been internally reflectedwithin the radiation passing layer, from impinging on the detector. Thisinternally reflected stray radiation (which is attenuated by theabsorber) may be caused by original radiation from the emitter that hasbeen internally reflected from oily build-up and residue, also referredto here as smudge, that has formed on the exterior surface of theradiation passing layer due to normal use of the device. As a result, amore accurate proximity sensor may be obtained.

The above summary does not include an exhaustive list of all aspects ofthe present invention. It is contemplated that the invention includesall systems and methods that can be practiced from all suitablecombinations of the various aspects summarized above, as well as thosedisclosed in the Detailed Description below and particularly pointed outin the claims filed with the application. Such combinations haveparticular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example andnot by way of limitation in the figures of the accompanying drawings inwhich like references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment of the invention in thisdisclosure are not necessarily to the same embodiment, and they mean atleast one.

FIG. 1 illustrates relevant portions of an electronic device, inaccordance with an embodiment of the invention.

FIG. 2 depicts an example mobile device in which an embodiment of theinvention can be implemented.

FIG. 3 is a sectional view along the line A, A′ of FIG. 2.

FIG. 4 is a sectional view of the proximity sensor arrangement,according to another embodiment of the invention.

FIG. 5 is a top view of an example radiation absorber.

DETAILED DESCRIPTION

Several embodiments of the invention with reference to the appendeddrawings are now explained. Whenever the shapes, relative positions andother aspects of the parts described in the embodiments are not clearlydefined, the scope of the invention is not limited only to the partsshown, which are meant merely for the purpose of illustration. Also,while numerous details are set forth, it is understood that someembodiments of the invention may be practiced without these details. Inother instances, well-known circuits, structures, and techniques havenot been shown in detail so as not to obscure the understanding of thisdescription.

FIG. 1 illustrates relevant portions of an electronic device, inaccordance with an embodiment of the invention. A sectional view of thedevice and, in particular, a region near its exterior surface is shownthat contains a radiation passage for a proximity sensor in the device.A radiation passing layer 2 separates an interior region of the devicefrom the outside where an external object is located nearby. Theradiation passing layer may be a cover or a cap which, as describedfurther below, may also be a structural layer (e.g., part of a frontfacing structural plate) of the device. It may be flat as shown orsomewhat curved, e.g. to provide a lens effect to the passing radiation.It may be made of a single material such as glass, ceramic,polycarbonate, or acrylic, or it may be a composite or laminate ofseveral layers of different materials. It may function as a protectivebarrier, and/or it may have an aesthetic function to provide a certainlook from the outside. In any case, the radiation passing layer 2 issufficiently transmissive in a radiation band of interest, and inparticular in this embodiment the infrared (IR) band, in order to permitan IR proximity sensor that is located below it to function as intended.An instance of the radiation passing layer 2 is the structural layer 11described below in connection with FIG. 3.

The proximity sensor includes an emitter 3, which emits the radiation(here, IR) and a counterpart detector 4, which is designed to detectimpinging radiation. The emitter 3 and the detector 4 have theirsensitive surfaces aimed at the radiation passing layer 2, eitherdirectly or indirectly (e.g., through a prism or mirror arrangement).Both are controlled and/or sensed electrically by proximity sensorcircuitry 5. This combination of the emitter, detector and proximitysensor circuitry may be a conventional, microelectronic infraredproximity sensor unit, e.g. an IR light emitting diode (LED)-based unitwith a built-in light collector (lens), analog to digital conversioncircuitry, and a digital communication interface to a processor (notshown). The detector may be part of a shared microelectronic device thatcan also be used to detect in other radiation bands, e.g. visible light.The data processor may be running proximity software that analyzesreadings or samples from the proximity sensor circuitry 5, based on whathas been emitted and what has been detected (as scattered or reflectedradiation from the external object). The proximity software may thenmake a determination as to whether the external object is close, far, orin between.

Between the emitter 3 and the detector 4 is a radiation shield 7 thatextends upwards to the bottom surface of the radiation passing layer 2,as shown. The shield in this case has a simple solid or polyhedronshape, but alternatively may have a more complex shape such as aT-shape. At its bottom, the radiation shield 7 may be secured to a frame(not shown) or a printed circuit board (not shown) on which the emitter3 and the detector 4 are also installed.

The shield 7 serves to block stray radiation originating from theemitter 3, i.e. by at least reflecting stray radiation but may alsoabsorb some of it to a limited extent. The shield's top surface could beaffixed to the bottom surface of the radiation passing layer, e.g. byvirtue of being glued or bonded to the bottom of an absorber 8;alternatively, its top surface could simply rest against the absorber 8,and be affixed at its bottom to a printed circuit board or othersubstrate or platform on which the proximity sensor is installed. Theshield 7 could be a structural wall that can bear a vertical load;alternatively it could just be a fence. An instance of the shield 7 isthe frame member 14 described below in connection with FIG. 3

As seen in FIG. 1, the top surface of the shield 7 conforms to thebottom surface of the radiation passing layer 2, by virtue of being incontact with and conforming to an absorber 8. The radiation absorber 8may be a separate piece and of a different material than the shield 7,and is positioned to provide a radiation seal between a top surface ofthe shield 7 and the bottom surface of the radiation passing layer 2. Agap-free joinder of the three components (the shield 7, the absorber 8,and the radiation passing layer 2) is desired in order to provide aproper radiation seal along the shield, in a horizontal or “Z” directionthat is perpendicular to the plane of the sectional view shown inFIG. 1. This may be achieved by having the surfaces of those componentsconform to each other as shown. In addition, the absorber 8 may bebonded to the bottom of the radiation passing layer 2 via an adhesivelayer (not shown in FIG. 1) that contains an index-matching materialwhich reduces the difference in refraction index (for the radiation bandused by the proximity sensor) between the absorber 8 and the radiationpassing layer 2.

The absorber 8 covers the adjoining surfaces of the radiation passinglayer 2 and the shield 7 but leaves open and separates two areasdirectly above the emitter 3 and the detector 4, respectively. Thispermits transmitted radiation and reflected/scattered radiation to pass,in this case in a substantially vertical direction, through theradiation passing layer 2 as shown, enabling the proximity sensor towork. The absorber 8 could be an otherwise continuous layer having twoholes formed therein as shown in the top view of FIG. 5. The absorber 8has a thickness in the vertical direction, and a width and length in thehorizontal directions so as to sufficiently absorb stray radiation thathas been internally reflected in the radiation passing layer 2 (which isdepicted as a dotted line labeled “B” in the figures). The internalreflections (B) may begin at the top surface of the radiation passinglayer 2 on which there may be a buildup or residue (on the exteriorsurface of the electronic device). This build-up or residue may be dueto contact with a user's skin during normal use of the device, which mayleave an oily film that also catches dust particles, thereby leaving abuild-up which may facilitate the undesired internal reflections (B)within the radiation passing layer 2. The absorber 8 may be expected tosignificantly attenuate such undesired reflections, without inhibitingthe desired reflections, such as those depicted as “A”, from reachingthe detector 4. In other words, the absorber 8 helps in reducing thestray radiation that would otherwise be able to get around the shield 7via the path “B” as shown (and impinge on the detector 4). This may helpthe proximity sensor circuitry 5 to operate more accurately whenproviding a measure of the external object scattered or reflectedradiation.

In one embodiment, the absorber 8 has the following characteristics inan infrared band 700 nm to 1,100 nm: transmittance less than fivepercent (5%), and reflectance less than ten percent (10%). Suchcharacteristics may be achieved by a film or sheet that is made ofpolyester or plastic. More generally, the film or sheet should havegreater infrared absorption characteristics than the radiation shield 7(for the same thickness and its other dimensions). In one instance, theabsorber 8 is made of a film or sheet that is of a different materialthan the shield 7. The shield 7 may need to achieve other purposes (suchas strength and low cost) that might sacrifice its radiation absorptioncharacteristics. For instance, the shield 7 may be particularly rigid(e.g., made of metal or a high strength plastic) and therefore unable tofunction as a radiation absorbing seal while being directly in contactwith the bottom surface of the radiation passing layer 2. One reason maybe that it cannot conform sufficiently to the bottom surface of theradiation passing layer 2 in a horizontal plane, in order to avoid anygaps. The presence of gaps may allow radiation to pass between theemitter side and the detector side, in the form of internal reflectionsthat are not sufficiently attenuated. Another reason for the inadequacyof the shield 7 acting by itself may be that it is of a material thatdoes not have sufficiently high radiation absorption characteristics. Bycombining the shield 7 and the absorber 8, together they may form abarrier that has essentially no radiation gaps between the bottomsurface of the light passing layer at one end, and the emitter and/ordetector at another end.

As depicted in FIG. 5, the absorber may be formed as a mask that has twoholes formed therein at positions that are directly above the emitter 3and the detector 4 (once installed in position). It may be a film orsheet that is to be joined to the bottom surface of the radiationpassing layer 2, and/or to the top surface of the shield 7. Forinstance, the sheet may be attached by an intermediate adhesive layer,such as a double-sided piece of tape or a thin layer of infraredtransmissive adhesive fluid; as a film it may be deposited or rolledonto the bottom surface of the radiation passing layer 2 in the form ofa liquid or gel which is then allowed to cure while in contact with thetop surface of the shield 7. Other ways of manufacturing the stackedarrangement of the radiation passing layer 2, the absorber 8, and theshield 7 may be possible.

Turning now to FIG. 2, an example mobile device 10 in which anembodiment of the invention can be implemented is shown. This particularexample is a smart phone having an exterior housing that is shaped andsized to be suitable for use as a mobile telephone handset. The mobiledevice 10 may be a personal wireless communications device that allowstwo-way real-time conversations (generally referred to as calls) betweena near-end user that may be holding the device 10 against her ear, and afar-end user. There is a connection over one or more communicationsnetworks between the mobile device 10 and a counterpart device of thefar-end user. Such networks may include a wireless cellular network or awireless local area network as the first segment, and any one or more ofseveral other types of networks such as transmission controlprotocol/internet protocol (TCP/IP) internetworks and plain oldtelephone system networks. The near-end user listens to the call usingan earpiece speaker located within the housing of the device and that isacoustically coupled to an acoustic aperture 12 formed near the top ofthe housing. The near-end user's speech may be picked up by a microphonewhose acoustic aperture 9 is located near the bottom of the housing.Also included in the housing are conventional electronic components suchas an audio codec circuit that interfaces transducers such as thespeaker and the microphone with digital audio signal processingcomponents. The audio codec circuitry may also allow the user to listento the call through a wireless or wired headset that is connected to thehandset portion of the mobile device 10. The call may be conducted byestablishing a connection through a wireless network, with the help ofRF communications circuitry coupled to an antenna that are alsointegrated in the housing of the device 10.

A user interacts with the mobile device 10 in this case by way of atouch screen that is formed in the front exterior face or surface of thehousing. The touch screen may be below the acoustic aperture 12(earpiece speaker), and above the acoustic aperture 9 (microphone). Asan alternative, a physical keyboard may be provided together with adisplay-only screen, as used in earlier cellular phone devices. Asanother alternative, the housing of the mobile device 10 may have amoveable component, such as a sliding and tilting front panel, or aclamshell structure, instead of the chocolate bar type depicted. FIG. 2also depicts a graphical user interface of a telephony applicationprogram that is running in the device 10 (e.g., stored in non-volatilesolid state memory and being executed by an applications processor). Thegraphical user interface causes a virtual telephone keypad to bedisplayed as shown, together with related virtual buttons that can beactuated by touch events of the near-end user initiating a call,accessing a stored contacts list of the user, and accessing a voicemailbox of the user.

In one instance, the wireless telephony handset (shown here as themobile device 10) has a structural layer 11 that may be a rigid, visiblelight transparent plate that begins at the top of the housing as shownand may extend down towards the bottom, forming most of the exteriorfront face of the housing and acting as a protective cover for the touchscreen. The structural layer 11 is an infrared light passing layer whosetop face is part of the exterior face of the housing, and whose bottomface is inside the housing (not shown). In this case, the structurallayer 11 also serves as an outer protective layer of the touch screenand is therefore transparent in the visible band as well. A proximitysensor having an infrared emitter and an infrared detector bothpositioned below the bottom face of the structural layer 11, inside thehousing, are located directly underneath the apertures indicated bydotted lines in FIG. 2. In the plane defined by the front exterior faceof the mobile device 10, these infrared apertures are located above thevirtual telephone keypad that is being displayed by the touch screen,closer to the acoustic aperture 12 (earpiece speaker) than the acousticaperture 9 (microphone). A sectional view of a relevant region insidehousing along the lines A, A′ is shown in FIG. 3.

As seen in FIG. 3, the acoustic aperture 12 is formed in the structurallayer 11, to the side of a region through which infrared radiation willpass for operation of the proximity sensor. An internal frame member 14is positioned between the emitter 3 and the detector 4, where the framemember 14 (as an instance of the shield 7, see FIG. 1) serves to blockinfrared radiation between the emitter and the detector. In addition,the internal frame member 14 may be designed (with the appropriate sizeand shape, as well as material) to assist in maintaining a rigid overallhousing structure, by serving as a weight bearing column or wall,against the bottom surface of the structural layer 11. The frame member14 extends upwards to the bottom face of the structural layer 11 whereit meets a radiation absorber 8 formed between a top surface of theframe member 14 and the bottom surface of the structural layer 11. Theframe member extends continuously upward and joins the bottom face ofthe structural layer 11 through the absorber 8, in order to form a wallthat has no infrared radiation gaps between the bottom surface of thestructural layer 11 and the emitter and detector. In this case, theframe member has a T-shaped cross section as shown, where the absorber 8conforms to the top of the T-shape cross-section. The absorber 8 (asdescribed above in connection with FIG. 1) serves to absorb theinternally reflected infrared radiation (originating as rays “B” thatwould otherwise make their way to the detector 4 as indicated by adotted line), where such may have been caused by buildup or residueshown on the top face of the structural layer 11. This reduces theamount of stray radiation that impinges on the detector 4, which mayincrease the accuracy of the proximity sensor. Note that the emitter 3and the detector 4 have been installed, in this example, on the samemicroelectronic or printed circuit board carrier, which may be a rigidprinted circuit board piece. Other options for installing thesecomponents of the proximity sensor within the housing of the mobiledevice 10 are possible.

In this case, the proximity sensor arrangement, including the absorber8, has been integrated in the mobile device 10 in such a way as toprovide the mobile device 10 with an external look that is uniformlydark. This may be achieved by the following arrangement of layers. Avisible light opaque layer 13 (that may have a dark color such as black)is formed in contact with the bottom face of the structural layer 11,with an opening therein aligned with the emitter 3 and another openingaligned with the detector 4. The layer 13 may be a black ink layer(which is opaque in the visible band) that has been deposited or rolledonto the bottom surface of the structural layer 11 and allowed to cure,while the openings have been masked off. This layer 13 gives theexterior face of the device 10 a uniform and dark look from the outside(as the structural layer 11 may be transparent in the visible band). Apurpose of the openings in the layer 13 is to allow infrared radiationto pass, as needed by the proximity sensor, because the black ink layermay not have sufficient transmissivity in the infrared band. Next, an IRtransmissive layer 15 that is opaque in the visible band is applied tothe bottom surface of the layer 13 as shown, also filling the openingstherein. The IR transmissive layer 15 may be a film of IR transparentpaint (also referred to as IR transmissive paint or ink, e.g. a dark orblack ink) that has been deposited or rolled onto the back of bottomface of the structural layer 11. The layer 15 serves to give a uniformappearance to the exterior face of the housing, by hiding the openingsthat have been formed in the layer 13. Next, the absorber 8 is appliedover the IR transmissive layer 15 as shown. As described above inconnection with FIG. 1, the absorber 8 may include a Mylar® film orsheet that is separate from but has been joined to the bottom surface ofthe structural layer 11 (in this case over the visibly opaque layer 13and the IR transmissive layer 15); alternatively, it may be joined tothe top surface of the frame member 14, prior to being brought intocontact with the bottom of the structural layer 11. The film or sheetmay be a polyester film or a plastic sheet that has greater infraredabsorption characteristics than that of the frame member 14, for thesame dimensions, e.g. thickness in the vertical direction. For instance,the absorber may have a transmittance of less than five percent (5%) anda reflectance of less than ten percent (10%), in an infrared band 700 nmto 1,100 nm. As an alternative, the infrared band may be slightly wideror narrower, but the transmittance should be about less than 5% and thereflectance should be about less than 10% in such bands.

FIG. 4 shows another embodiment of the invention where the absorber 8 iscomposed of an infrared passing adhesive layer 16 (e.g., an opticallyclear adhesive fluid) in contact with the top face of an absorbing layer17 (e.g., a Mylar® sheet patterned as shown in FIG. 5). The adhesivefluid may be an index matching material that reduces differences inindex of refraction (within the infrared band used by the proximitysensor) between the absorber 8 and the radiation passing layer 2 orstructural layer 11. The two holes may actually be physical holes madeonly in the absorbing layer 17, and not in the infrared passing adhesivelayer 16, and are aligned with the locations of the emitter 3 and thedetector 4 (which may be directly below these holes). Alternatively, theadhesive layer 16 may be applied only to the top face of the patternedpiece (absorbing layer 17). The absorber 8 is then pressed against thebottom surface of the radiation passing layer 2 or structural layer 11,to form the arrangement as shown. Note also a difference in this case,relative to the embodiment of FIG. 3, in that there is a single, largeropening formed in the visibly opaque layer 13, which encompasses theemitter and the detector regions as well as the separating regionbetween them. Accordingly, the visibly opaque infrared transmissivelayer 14 will in this case fill the entirety of such opening as shown,in order to maintain the desired uniform dark look from the exterior.The structure in FIG. 4 may be otherwise the same as that of FIG. 3.

What has been described above is an electronic device having an externalhousing in which the constituent components of the device are located, aradiation passing layer or structural layer (also referred to here as acover) that physically protects the electronic components while allowingradiation to pass therethrough, a proximity sensor that transmitsradiation out of the housing and receives radiation that has beenscattered outside of the housing, and a shield that blocks strayradiation from impinging on the detector portion of the proximitysensor. An absorber is positioned between the shield and the bottomsurface of the cover in a way that removes radiation gaps and serves totake up stray radiation, that may be due to internal reflections withincover, such as those caused by smudge on the exterior face of the cover,in order to prevent such from impinging on the detector portion of thesensor. A method for manufacturing such an electronic device may proceedas follows.

Referring to FIG. 3 and FIG. 4, a bottom or rear face of a transparentcover or cap (an instance of the structural layer 11 or radiationpassing layer 2) is prepared to receive a coat of visibly opaque (dark)paint thereon. One or more paint masks that are located directly abovethe positions of an emitter and a detector of a proximity sensor areapplied to the prepared surface. The dark paint layer is then appliedand allowed to cure. The mask is removed thereby exposing the bottomsurface of the cover at the IR apertures, which will be located directlyabove the emitter and the detector. A visibly opaque infraredtransmissive layer (e.g., a coat of IR transmissive black ink) isapplied to the exposed IR apertures, and is then allowed to cure.Finally, an absorber is applied as either a single film or as amulti-layer structure, with openings that are aligned with those in theoriginal black paint layer. For instance, an IR clear adhesive may beapplied to a top face of an IR absorbing layer 17 that has separatephysical openings formed therein for the emitter and the detector, whichis then adhered to the IR transmissive layer 15. Alternatively, the IRclear adhesive may be applied to the bottom of the cover (over the IRtransmissive layer 15), and then the IR absorbing layer 17 is pressedonto the bottom of the cover against the adhesive. Additional operationsmay be needed prior to the above or thereafter, before the cover hasbeen completed and is ready to be installed into the housing. At thatpoint, the cover is positioned into the housing, with its IR aperturesand openings aligned to the emitter and the detector locations, and isbrought into contact with the top surface of the internal frame member14. The cover is then fixed in that position and becomes the exteriorfront face of the housing.

While certain embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat the invention is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those of ordinary skill in the art. For example, although themanufacturing process has been described in connection with theembodiments of FIG. 3 and FIG. 4, a similar process can be gleaned forthe embodiment of FIG. 1 in which no visibly opaque layers may benecessary. Also, while the drawings depict different layers being incontact with each other (e.g., in FIG. 3, layer 13 is in contact withthe bottom of layer 11, and the absorber is in contact with the layer15), this does not preclude an additional or intermediate layer betweenthem so long as the purposes of the radiation seal achieved by theabsorber 8, including that of attenuating the stray internal reflectionswithin the layer 11, are not thwarted. The description is thus to beregarded as illustrative instead of limiting.

What is claimed is:
 1. An electronic device comprising: a radiationpassing layer having a top surface and a bottom surface; a proximitysensor having a radiation emitter and a radiation detector, bothpositioned below the radiation passing layer; a radiation shieldpositioned between the emitter and the detector, and extending to thebottom surface of the radiation passing layer; and a radiation absorberbeing a separate piece and of a different material than the shield andpositioned to provide a radiation seal between a top surface of theshield and the bottom surface of the radiation passing layer wherein theabsorber is formed as a mask that has two holes formed therein directlyabove the emitter and the detector, respectively.
 2. The device of claim1 wherein the absorber comprises a film or sheet that is separate frombut that has been joined to at least one of the bottom surface of theradiation passing layer and the top surface of the shield.
 3. The deviceof claim 2 wherein the film or sheet is of a different material than theshield.
 4. The device of claim 2 wherein the film or sheet is made of amaterial that has greater infrared absorption characteristics than thatof the radiation shield.
 5. The device of claim 2 wherein the film orsheet is one of a polyester film and a plastic sheet.
 6. The device ofclaim 1 wherein the absorber has the following characteristics in aninfrared band 700 nm to 1100 nm: transmittance less than 5% andreflectance less than 10%.
 7. An electronic device comprising: awireless telephony handset housing having an infrared light passinglayer whose top face is part of an exterior face of the housing andwhose bottom face is inside the housing; a proximity sensor having aninfrared emitter and an infrared detector both positioned below thebottom face of the light passing layer, inside the housing; an internalframe member positioned between the emitter and the detector, the framemember to block infrared radiation between the emitter and the detector;and an infrared absorber being a mask that is of a different materialthan the frame member and has two holes formed therein, wherein the maskis positioned between a top surface of the frame member and the bottomsurface of the light passing layer such that the two holes are directlyabove the emitter and the detector, respectively.
 8. The device of claim7 wherein the internal frame member extends continuously upward andjoins the bottom face of the light passing layer through the infraredabsorber.
 9. The device of claim 7 further comprising an earpiecespeaker and a microphone both inside the housing, a top face to bottomface acoustic aperture formed in the light passing layer andacoustically coupled to the earpiece speaker, and wherein the proximitysensor is positioned closer to the aperture than the microphone.
 10. Thedevice of claim 7 wherein the light passing layer is flat, the framemember has a T-shape, and the absorber conforms to a top of the T-shape.11. The device of claim 7 wherein the absorber comprises a film or sheetthat is separate from but that has been joined to at least one of thebottom surface of the light passing layer and the top surface of theframe member.
 12. The device of claim 11 wherein the film or sheet isone of a polyester film and a plastic sheet that has been bonded to thelight passing layer via an adhesive containing an index-matchingmaterial.
 13. The device of claim 11 wherein the film or sheet is madeof a material that has greater infrared absorption characteristics thanthat of the frame member.
 14. The electronic device of claim 7 whereinthe absorber has the following characteristics in an infrared band 700nm to 1100 nm: transmittance less than 5% and reflectance less than 10%.15. The electronic device of claim 7 further comprising a touch screenwhose top face is part of the exterior face of the housing, and whosebottom face is inside the housing.
 16. The electronic device of claim 15wherein the infrared light passing layer forms part of and is an outerprotective layer of the touch screen as well as a structural layer ofthe housing.
 17. The electronic device of claim 7 further comprising: avisible light opaque layer in contact with a bottom face of the lightpassing layer and having an opening therein aligned with one of theemitter and the detector; and an infrared transmissive layer in contactwith the bottom face of the light passing layer within said opening, togive a uniform appearance to the exterior face of the housing, whereinthe absorber is joined to the infrared transmissive layer.
 18. A methodfor manufacturing an electronic device, comprising: applying an infraredabsorber being a mask having two holes formed therein, to the bottomsurface of a radiation passing layer; and then positioning the radiationpassing layer into an exterior housing of a mobile device and fixing theradiation passing layer in place while the absorber is in contact with atop surface of an internal frame member in the housing that lies betweenan infrared emitter and an infrared detector of a proximity sensor inthe housing, such that the two holes of the mask are aligned with aradiation passage for the emitter and the detector, respectively. 19.The method of claim 18 wherein the absorber has the followingcharacteristics in an infrared band 700 nm to 1100 nm, namelytransmittance less than 5% and reflectance less than 10%.